Taking the stage in Milwaukee at the Marcus Amphitheatre, he thanked Perry for helping him take on the vocal chord problems that left him silent for about 20 months. (He didn't perform live for the first time until this past January.)

"She was so patient," he told the audience of his on-again girlfriend, who ordered food for him when he couldn't speak. He said she took the time "to continue to get to know me and love me," despite his health issues.

The tune in her honor? "A Face to Call Home," a soft love song off his 2012 album Born and Raised.

Closing with the ballad, Mayer – who first stepped out with the pop star last August before breaking up most recently in March – said the song was for "Katy, who is my face to call home."